The estimated ticket revenue lost over that time is a whopping $42 million.

The ridership drop is being chalked up to two recent trends: the rise in ride services such as Lyft and Uber and the growing concern among customers about their personal safety.

In recent years BART, like much of the rest of the Bay Area, has been hit with a wave of property crimes, including cell phone snatchings. There has also been a rise in the number of homeless people using the stations and trains as makeshift shelters.

There has also been a string of high-profile crimes, such as in 2017 when 40 to 60 teens took over a train car at the Coliseum Station and forced passengers to hand over bags and cell phones.

More recently, there was the fatal slashing of 18-year-old Nia Wilson as she was about to get on a train at MacArthur Station in Oakland, though officials say they haven’t seen any additional significant drop in ridership since the stabbing.

After Wilson was killed, BART police beefed up patrols throughout the 48-station system, but overall it continues to have one officer on patrol for every two or three stations.

“We need to implement better security as quickly as possible if we are going to regain the confidence of riders or attract new riders,” said BART Director Joel Keller, whose district includes the Contra Costa County suburbs.

And while safety is in the news these days, Raburn and others say BART trains running only once every 20 minutes on nights and weekends is also a problem.

“That’s not convenient for a lot of people,” Raburn said. Especially if the rider needs to change trains.

“If you miss your connection, you can be waiting another 20 minutes,” he said.

Cutting down on those wait times for trains, however, could be difficult.

BART performs maintenance on the cars during evenings and weekends, so running more trains on the off-hours could mean fewer trains for the already-packed peak hours.

Raburn said the answer is more cars — which should be arriving in the next year.

Keller agreed that more cars are essential, but he said more police are needed as well.

“Otherwise,” he said, “the trend is going to continue.”

Riding the wave: The race is on for ride-service companies to deliver self-driving cars to the already congested streets of San Francisco, possibly as early as next year.

The result has been a hiring binge as the companies snap up former City Hall staffers and consulting firms to help navigate any regulatory roadblocks — particularly on safety issues.

Uber, for instance, has brought on David Noyola, a former aide to Supervisor Aaron Peskin, who only recently cut a tax deal with the ride companies that could net the city millions of dollars for traffic improvements.

Jess Montejano, a former senior adviser and confidant to former Mayor Mark Farrell, signed on as vice president at Riff City Strategies, a local public affairs firm that’s helping General Motors’ Cruise Automation.

Cruise Automation already is testing self-driving Chevy Bolts and is angling to become the only company in eco-friendly San Francisco with an entire fleet of electric cars.

It’s actually the state Public Utilities Commission that will issue the permits for companies to operate here, but the city will have a say in how they operate and is considering safety and curb-use regulations.

“Safety is the first, second and third most-important issue,” said Montejano, saying that self-driving vehicles will actually make the roads safer for everyone “by reducing the 94 percent of car crashes each year that result from human error.”

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX-TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call 415-777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross